Abstract

This paper investigates static properties of laser welded ultra-high-strength (UHS) stainless steel tube. The material of the tube was cold-hardened ultra-high-strength austenitic stainless steel (AISI 301 2H) with a tensile strength of 1.55 GPa. The AISI 301 steel tubes were manufactured by laser welding from two U-shaped parts. For comparison, low strength stainless steel (AISI 304) tubes were also examined in the experiments. The microstructure of the welded joints was studied by optical microscopy. The hardness of the laser weld joint was determined. The strength of the tubes was studied by three-point bending and compression tests. It was observed that the hardness at the HAZ of the AISI 301 joint was 51% lower than that of the base material. HAZ showed new fine grains of austenite phase structure due to the reversion transformation from martensite to austenite. Result showed that the AISI 304 weld had the same hardness as the base material. Three-point bending experiments revealed that the bending strength of the UHS (AISI 301) steel tube was approximately 60% higher than that of low strength AISI 304 steel tube. The location of the weld relative to the direction of the compressive force had a significant effect on the compressive strength of the UHS (AISI 301) steel tube.